Fundamentals of Computing - Lesson 5 - The Speed of CPUs and Harddrives

In this lesson we will look at the speed of CPUs the the role harddrives play in the overall system performance. Once again, we will be sure to remember that some aspects are historic, but they give you a pretty good idea of why there is a price difference between slower and faster systems.

No one could doubt there was a difference between slower and faster systems, but at times the numbers behind the ads may confuse you.

When talking about harddrives, you have TWO essential numbers besides the actual harddrive size, and these are:

RPM - Rounds Per Minute: The number of circulations your harddrive takes per minute
Cache: The amount of memory that caches data when you read from your harddrive

Rounds Per Minute - What Does This Mean?
First of all, please take a look at this video which explains a bit about the idea of rounds per minute, before we continue:


The number of rounds per minute is not in itself a determining factor, as you could see on the video. If you are going to build a desktop computer heat and power consumption won't really be an issue, but certainly could be if you are going to build a laptop. In fact, fixed disc drives will be the future - for some models already is - as there is nothing that rotates, and thus uses even less power.

We will take a look at two harddrives:

- Seagate Momentus Thin ST500LT012 500 GB - 5400 rpm - Interface: Serial ATA-300 - Buffer: 16Mb
- MicroStorage Harddisk 160 GB - 7200 rpm - Interface: IDE - Buffer: 8Mb

If you hadn't watched the video, you would probably believe the MicroStorage harddrive would be the fastest, but the transfer rates are as follows:

Seagate: 300 MBps
MicroStorage: 133 MBps

Which brings me to the next thing, the cache:

How Big a Cache Do I Need?
In the old days, some harddrives were only mounted with 1Mb of cache, and as you can see above 8Mb and 16Mb are now the standard of the day - and some have even larger caches.

It's all a matter of price. The first thing you need to do when you see a computer you want is to check reviews, and hopefully these will have benchmarks, so you can compare which system is the best.

What Is the Relationship With Your CPU?
There is no need to have a super quick CPU if you have a sloppy harddrive. Your bus will be busy transferring data, and you won't get the best from your CPU. Similarly, if you have a good CPU, a graphics card that isn't delivering optimal performance won't give you a fast system.

Therefore, you need the best in comparison for what types of tasks you are doing. If you are an author, and most of your work is based around word processing, your system may be fine. But when your child borrows your computer to run World of Warcraft or some other graphics intensive games, your computer will be too busy doing everything but deliver what you want. This will be seen in poor screen resolution with a less than perfect graphics quality because your system is lacking in real basic power.

In the next lesson we will be looking at your network - what are the differences between cabled networks and WiFi?